Mazut is a heavy fuel oil primarily used in industrial settings, such as power plants, heating plants, and large-scale boilers. It is often used as a fuel for generating electricity and as a heat source in manufacturing processes. Due to its high energy content and relatively low cost, mazut is a popular choice in regions where natural gas or lighter fuels are less accessible or more expensive. However, its use is declining in some areas due to environmental concerns and the push towards cleaner energy sources.